Jump to content

Calibrate 800k/1.4mb Floppy drives 3.5"

Recommended Posts

Good morning all, 

Is there instructions or tutorial regarding calibrating those 3.5" floppy disk drives?

I've seen the video about lubricating it - but Is there specific point that the heads or sensor needs to be calibrated?


I've got a stack of 7x 1.4mb and 2x 800k are not working/won't read/format or spits out - Too many drives that are non working sitting there, and I want them fixed!


NB: All moving parts have been cleaned/lubricated.




Share this post

Link to post
Share on other sites

Oh man, I hope you get an answer to this. I tried to figure this problem out a few years ago and never got anywhere, but it was around the time I drifted away from the hobby. I will be watching this thread eagerly.

Share this post

Link to post
Share on other sites

Need to inspect the heads under a magnifier and look at the head gap versus a good drive. Most of the time these things wear clean out.  Calibration doesnt drift unless its been physically dropped hard. 

Edited by techknight

Share this post

Link to post
Share on other sites

I guys,

I'll also interested in this topic.


I read generally about a calibration procedure:

Attaching oscilloscope probes to the heads cable (there are fours stripes for each head,  do not know which are the one)

Insert a reference floppy and read it

Adjust the heads alignment until you have the maximum signal


It is a starting point, but it's too vague to me, and I do not want to buy an oscilloscope just for a test


I still hope to find a way to calibrate the heads, any news here?



all the best


Share this post

Link to post
Share on other sites

Larry Pina's books often have procedures for aligning floppy drives without lots of the specialized test equipment that Sony requires for a factory calibration. Try checking your local library for The Dead Mac Scrolls or any flavor of Macintosh Bible that he's published if you want a good walk through.


From my memory, the basic procedures (for Sony manual inject only, though it should work on auto inject drives):


You'll need a certified good Mac floppy for testing, either factory produced or formatted on a known-good Mac, to use for alignment. Make sure the disk is LOCKED or you will ruin it and/or screw up the alignment process.

You will need full access to the drive while it is operating so don't try to do this in situ on a SE or Color Classic; you really should use an LC or II of some sort, better yet if you can fabricate a very long floppy cable so that you can have the drive connected outside of the computer and thus have lots of room to work on the drive. 

Also, clean the drive first, including the heads, to eliminate dirt as the cause of your problems.

This procedure assumes the drive hasn't been damaged and isn't missing pieces.


For track-0 alignment (generally only necessary if the drive has been completely disassembled and the drive asks to format every disk):

There's a post on the side of the head assembly (an interrupter) on the side opposite of the motor, and it slides into a slot in a black plastic thing (the optical assembly) toward the back of the drive. The interrupter interrupts an optical beam when the head assembly moves into position, and when this happens the drive knows that it is at track 0. To adjust this, mark the current position of the optical assembly, slightly loosen the screws securing the optical sensor assembly, move the assembly slightly forward or back, tighten the screws, and then insert a disk. Repeat the process until the computer attempts to read the disk rather than simply saying it's "not a Macintosh disk." If the head alignment hasn't been bothered, this should be all you need to do as the drive will be properly aligned to track 0 and thus be able to read a good disk. However if the computer has problems reading the disk even after adjusting the setting for track 0, you'll need to adjust the head alignment.


For head alignment (for a drive with new heads, that has been completely disassembled, or regularly has problems reading manufactured disks or disks formatted on other computers/other computers can't read disks formatted in this drive):

There are two hex screws on either side of the stepper motor that drives the heads. Mark the current orientation of the drive chassis to the stepper motor body. Loosen these screws slightly and turn the motor body slightly one way or the other. Insert a disk and wait for the computer to respond. If it says the disk has problems, eject the disk, twist the drive motor body a little more in that direction, and reinsert the disk until the computer reads it reliably. If it instead says the disk is unreadable, try rotating the drive motor in the other direction until the drive attempts to mount the disk. Usually you would rotate the motor body until the drive starts to read the disk well, mark the position, then keep rotating it until it no longer reads the disk, mark the position again, and then rotate it back to a middle point between where it starts and stops reading the disk properly before tightening the screws. This usually ensures the best drive performance and is as good as it gets without getting into crazy test equipment.

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now